Tire tread



Aug. 10, 1965 G. KUNZ ETAL 3,199,567

TIRE TREAD Filed Dec. 30, 1963 2 Sheets-Sheet l IN VEN TORS GERALD K UNZ BYSAMUEL E. STOVERI Aug. 10, 1965 G. KUNZ ETAL 3,199,567

TIRE TREAD Filed Dec. 30, 1965 2 Sheets-Sheet 2 INVENTORS GERALD KUMZ BYSAMUEL E. STovER United States Patent 3,19%,56'7 THREE TREAT) Gerald Knnz, Cuyahoga idaiis, Ohio, and amnel E. Stoves, Grahill, Ind, assignors to The B. Goodrich Company, New York, N.Y., a corporation of New York Filed Dec. 30, 1963, Ser. No. 334,378 4 Claims. (Cl. 152-209) a This invention relates to improvements in the traction pattern of the elastomer tread for a pneumatic tire and, mordparticularly, to the formation in the traction pattern of the tire tread of slit-like grooves that have a configuration at the tread surface which differs from that at a location radially inwardly of the surface. The mold members for forming the traction pattern, as herein disclosed, are claimed in our copendin divisional application Serial No. 447,337, filed April 12, 1965.

Pneumatic tires for vehicles now customarily have the elastomeric running surface or tread provided with a traction assisting pattern comprising load-bearing portions separated by grooves of appreciable width. In addition, the load-bearing portions are frequently provided with with slit-like grooves or kerfs to increase the edge areas of the load-bearing portions and thereby improve the traction and other desirable characteristics of the tread pattern. There kerfs or slit-like grooves have, however, occasioned annoyance and damage as the result of picking up small stones and other hard objects. Thus, these foreign objects while adjacent the surface of the tread cause irritating noise during rotation of the tire on a paved surface. When such objects are not removed, they have frequently worked or drilled radially inwardly of the tread during continued use of the tire resulting in damage to it.

In accordance with this invention, the traction pattern in the elastomer tread of a pneumatic tire has slit-like grooves formed therein which have the sidewalls of at least a part of these grooves, radially inwardly of the tread surface, formed with undulations or corrugations extending in the direction transverse of the depths of the grooves while the edge portions of said grooves at the tread surface are devoid of the said undulations or corrugations. This configuration of the slit-like grooves resists entrance of small stones and other foreign objects into the grooves and also facilitates expulsion of such objects as are picked up by the outer edge portions of the grooves. Moreover, the interlocking action of these un dulations or corrugations improves the lateral stability of the tread. Preferably, the said undulations or corrugations are of sinuous configuration and are produced by molding as the result of employing in the tire mold thin elongated members of appropriate configuration.

The nature of the invention is hereinafter further explained with reference to the accompanying drawings, forming a part of this application, in which:

FIG. 1 is a fragmentary perspective View of the presently preferred tire tread traction pattern incorporating the invention, the traction pattern continuing throughtout the circumference of the tire which is indicated by dot-dash lines;

FIG. 2 is an enlarged fragmentary portion of the traction pattern shown in FIG. 1 as it appears after a portion of the tread surface has been removed;

FIG. 3 is a side elevational view of one form of a bladelike member for molding the slit-like grooves in a tire tread;

FIG. 4 is a sectional view taken on the section indicating line 44 of FIG. 3;

FIG. 5 is a side elevational view of another form of blade-like member for molding the slit-like grooves and showing the member before it is bent to a configuration for use in a traction pattern of the configuration shown in FIGS. 1 and 2;

FIG. 6 is a sectional view taken on the section indicating line 66 of FIG. 5; and

FIG. 7 shows the manner in which the member of FIG. 5 is bent to a configuration appropriate for a traction pattern similar to that illustrated in FIGS. 1 and 2.

The tire tread 10, illustrated in FIG. 1, is formed of elastomeric material in which a traction pattern comprising load-bearing portions 11, separated by generally circumferentially extending grooves 12, is formed during the vulcanization of the tire The load-bearing portions 11 on either side of a central rib 13 are additionally provided with slit-like grooves or kerfs 14 which divide these load-bearing portions into a plurality of closely adjacent blocks that may be of desired configuration. As here shown, the blocks adjacent the central rib 13 are generally H-shape while the laterally adjacent blocks are diamond shape.

The slit-like grooves 14 are, in accordance with this invention, so formed that the edges thereof at the tread surface are a plurality of angularly intersecting straight lines which provide the desired tread pattern configuration. The sidewalls of at least the portions of these grooves comprising transverse boundaries of the H-shape and diamond shape blocks are, however, of nonlinear configuration in regions radially inwardly of the outer urface of the tread. Thus, as shown in FIG. 2, which illustrates a portion of the tread pattern of FIG. 1 after the radially outer surface thereof has been removed, the portions v15 of the grooves 14 have sidewalls of corrugated or undulating, preferably sinuous, configuration. The parts of the slitlike grooves 14 which provide boundaries between the leg portions of the H-shaped blocks may also be of similar configuration. However, in the illustrated embodiment, these portions of the slit-like grooves 14 have planar sidewalls throughout their depths.

The slit-like grooves 14 with their two dilferent sid wall configurations :are provided in the traction portion of the tire tread during molding by thin elongated mold members of appropriate configurations. In the preferred embodiment, these mold members are blade-like strips of metal one longitudinal edge portion of which has planar side faces while the other longitudinal edge portion is of undulating or corrugated cross section, preferably of sinuous configuration. Thus, as shown in FIG. 3, the mold member 16, which is utilized to form a slit-like groove 14 between two adjacent diamond shape blocks of the tread shown in FIGS. 1 and 2, is an elongated strip of sheet metal one longitudinal edge portion 17 of which has planar ide faces while the other longitudinal edge portion 18 has the sidewalls thereof in non-linear configuration as viewed in cross section. This non-linear configuration is preferably sinuous, as shown in FIG. 4, and extends from the edge portion 18 of the member 16 to a region short of the edge portion 17 where the sinuous configuration smoothly merges with the planar configuration. Preferably, the longitudinal extent of the planar edge portion 17 of the blade-like member 16 is greater than that of the non-linear edge portion 18.

The blade-like mold member 16 is employed by fixing it in the tread portion of a the mold with the planar edge portion 17 adjacent the mold surface so that this portion becomes the outer edge port-ion of the molded slit-like groove 14 in the tire tread. The longitudinal edge portion 18 is in radially projecting relationship with respect to the mold surface and therefore forms the base of the slit-like groove 14 in the completed tire. The manner of fastening the blade-like member 16 in a tire mold is well understood in the art and hence is not here illustrated nor described in detail.

The thin elongated mold members 19 for forming the other slit-like grooves 14 between the H-shape blocks in the tire tread are similar in general nature to the member 16 but specifically different in configuration to provide the requisite multi-angular configuration of these slitlike grooves in the tread pattern. As illustrated in FIG. 5, the thin elongated mold member 19 is formed as an elongated blade-like strip of sheet metal one longitudinal edge portion 20 of which is provided with planar side faces; Extending from this edge portion are spaced projecting segments 21 and 22 the sidewalls of which. are corrugated or undulating in cross section. This configuration, as shown in FIG. 6, is preferably sinous and, as shown in FIG. 5, extends from the longitudinal edge portions 23, 24 to a region adjacent the opposite edge portion 20 where the sinuous configuration of the sidewalls merges into the portion with the planar side surfaces. The segments 21, 22 of the member 19 are preferably spaced from each other and integrally connected by a portion 25 having planar Side surfaces and of less width than the segments 21, 22. It is also preferable that the planar sidewall portions of the member 19 extend longitud-inally beyond the segments 21, 22 and that these end portions of the member 19 be of greater width adjacent the segments than at the free ends.

The member 19, before insertion in the tire mold, is bent from the strip-like configuration, shown in FIG. 5, to the con-figuration appropriate for forming the slit-like groove 14 between the H-shape blocks. This configuration is illustrated in FIG. 7 wherein the member 19 has been shown inverted to facilitate illustration of the sinuous sidewall portions. After bending the member 19 to the appropriate configuration, it is inserted into the tire mold with the edge having the planar side surfaces 20 adjacent the mold surface as is the case for the mold member 16.

The thin mold members 16 and 19 are preferably provided with holes, such as 26, extending through the portions thereof having the planar sidewalls. These holes are for the purposes of facilitating venting of air and other gases in the molds during vulcanization of the tire. The location of these holes may be chosen as is necessary for eifective venting action and their presence or absence does not in any way afiect the principles of the invention.

A tire tread traction pattern having slit-like grooves as herein disclosed functions to prevent the entrance of foreign objects by reducing the freedom of these grooves in opening in response to attempted penetration by foreign objects. This feature, which is achieved by the corrugated or undulating configuration of the sidewalls of the grooves interiorly of the tread surface, does not, however, result in the appearance at the original tread surface of this configuration so that the new tires have the advantage of simplicity of pattern appearance while providing increased lateral stability due to the multiple surface interlocking sidewall configurations within the slit-like grooves. Furthermore, the presence of undulating or corrugated sidewalls in the grooves 14 acts upon any foreign bodies which attempt to penetrate the grooves in a manner which facilitates their dislodgement as the tire tread flexes in its rolling upon the road surface. This reduces the opportunity for foreign objects to be retained in the grooves sufiiciently to permit drilling thereof into the tread with resulting damage to the tire.

The thin mold members for forming the slit-like grooves 14 are preferably sheet metal stampings. The invention in its broader aspects, however, is not limited to mold members formed in this maner and inserted into a mold but is considered as inclusive of similar members cast or otherwise formed in the mold. Furthermore, the invent-ion is not limited to the illustrated configuration of the mold members nor to the particular tread pattern shown in the drawings. For example, the mold members 19 may have a generally serpentine configuration rather than the angular form illustrated in FIG. 7. These and other modifications and adaptions of the disclosed tread pattern, which will be readily apparent to those skilled in the art, are considered as encompassed within the ambit of the invention which is limited only by the spirit and scope of the appended claims.

Having thus described the invention, we claim:

1. In a pneumatic tire having an elastomer tread provided with a traction pattern including slit-like grooves, the improvement which comprises the sidewalls of at least a portion of said grooves radially inwardly of the tread surface being undulating in the direction transverse of the depth of the grooves while the edge portions of said grooves at the tread surface are devoid of the said undulations.

2. In a pneumatic tire having an elastomer tread provided with a traction pattern including slit-like grooves, the improvement which comprises the sidewalls of at least a portion of said grooves radially inwardly from the tread surface being corrugated in the direction transverse of the depth of the grooves while the edge portions of said grooves at the tread surface are devoid of the said corrugations.

3. In a pneumatic tire having an elastomer tread provided with a traction pattern including a plurality of tread elements at least some of which are separated from adjacent elements by slit-like grooves molded in the tread, the improvement which comprises at least portions of said grooves having corrugated sidewalls radially inwardly of the tread surface While the edges of said portions of the grooves at the surface of the tread are devoid of the said corrugations.

4. In a pneumatic tire having an elastomer tread provided with a traction pattern including slit-like grooves molded in the tread, the improvement which comprises the tread surface edge portions of said grooves lying in straight lines and the sidewalls of at least a portion of said grooves being sinuous in circumferential section radially inwardly of the tread surface.

References Cited by the Examiner UNITED STATES PATENTS 592,961 11/97 Brooks 30-355 2,587,297 2/52 Duerksen 18-44 2,621,698 12/52 Zohrer 152-209 2,834,108 5/58 Thompson 30-355 2,878,852 3/59 Lippmann et al. 152-209 3,100,318 8/63 Knox 18-44 ARTHUR L, LA POINT, Primary Examiner, 

1. IN A PNEUMATIC TIRE HAVING AN ELASTOMER TREAD PROVIDED WITH A TRACTION PATTERN INCLUDING SLIT-LIKE GROOVES, THE IMPROVEMENT WHICH COMPRISES THE SIDEWALLS OF AT LEAST A PORTION OF SAID GROOVES RADIALLY INWARDLY OF THE TREAD SURFACE BEING UNDULATING IN THE DIRECTION TRANSVERSE OF THE DEPTH OF THE GROOVES WHILE THE EDGE PORTIONS OF SAID GROOVES AT THE TREAD SURFACE ARE DEVOID OF THE SAID UNDULATIONS. 